The purpose of this study was to assess the effects of curriculum-based measurement (CBM), with and without diagnostic feed-back, on general and special educators' instructional planning in reading. Participants were 19 second-grade teachers with their 309 students without disabilities and 16 resource teachers with their 127 first-through fifth-grade students with mild disabilities. Blocking on background (general vs. special education), teachers were assigned randomly to three conditions: control, CBM, or CBM with diagnostic feedback (CBM+D). CBM data were collected on students for 3 consecutive weeks. Then teachers attended a 2-hour workshop where they completed classwide and individual student instructional planning sheets in accordance with their experimental condition. For the individual plans, one high-, one average-, and one low-performing student was selected from each teacher's class. On the classwide plans, across backgrounds, teachers in the CBM+D condition targeted fewer objectives than control teachers. On individual plans, CBM+D resource teachers targeted appropriate skills for average- and low-achieving students more effectively than did CBM and control resource teachers, and CBM+D second-grade teachers targeted appropriate skills for average- and highachieving target students more effectively than CBM second-grade teachers. Implications for future research and practice are discussed.